. Pharmaceutical botany. Botany; Botany, Medical. ,- 000 ^QOqO Fig. 20.—Cross-section through a lenticel of Sambucus nigra. E, Epidermis; PE, phellogen; L, loosely disposed cells of the lenticel; PL, cambium of the lenticel; PS, phelloderm; C, cortical parenchyma containing chlorophyll. {From Sayre after Strasburger.) cells, which function as passages for gases and watery vapor from and to the active cells of the cortex beneath. There very early originate in the region beneath the stomata loosely arranged cells from cork cambium which swell up during rain and rupture, forming convex fissures i
. Pharmaceutical botany. Botany; Botany, Medical. ,- 000 ^QOqO Fig. 20.—Cross-section through a lenticel of Sambucus nigra. E, Epidermis; PE, phellogen; L, loosely disposed cells of the lenticel; PL, cambium of the lenticel; PS, phelloderm; C, cortical parenchyma containing chlorophyll. {From Sayre after Strasburger.) cells, which function as passages for gases and watery vapor from and to the active cells of the cortex beneath. There very early originate in the region beneath the stomata loosely arranged cells from cork cambium which swell up during rain and rupture, forming convex fissures in the cork layer, called lenticels. The function of lenticels is similar to that of stomata, namely, to permit of aeration of delicate cells of the cortex beneath. Annual Thickening.—-In all woody exogenous stems such as trees and shrubs the persistent cambium gives rise to secondary xylem thickening every spring, summer and autumn. Soon a great cylinder of xylem arises which con- stitutes the wood of the trunk and branches. In the spring, growth is more active, and large ducts with little woody fibre are produced while in summer or autumn growth is. Fig. 21.—Part of a transverse sec- tion of a twig of the lime, four years old. m, Pith; ms, medullary sheath; x, secon- dary wood; Ph\ phloem. 2, 3, 4, annual rings; c, cambium; pa, dilated outer ends of medullary rays; b, blast; pr, primary cortex; k, cork. {From Sayre after Vines.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Youngken, Heber W. (Heber Wilkinson), 1885-1963; Stewart, Francis Edward, 1853-1941. Philadelphia, P. Blakiston's son & co
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